Polymeric tandem dyes with linker groups

ABSTRACT

Compounds useful as fluorescent or colored dyes are disclosed. The compounds have the following structure (I):or a stereoisomer, tautomer or salt thereof, wherein R1, R2, R3, R4, R5, Ll, L2, L3, L4, M1, M2, m and n are as defined herein. Methods associated with preparation and use of such compounds is also provided.

BACKGROUND Field

The present invention is generally directed to dimeric and polymeric chromophore compounds (e.g., polymer compounds comprising fluorescent dye moieties) having spacing groups, and methods for their preparation and use in various analytical methods.

Description of the Related Art

Fluorescent and/or colored dyes are known to be particularly suitable for applications in which a highly sensitive detection reagent is desirable. Dyes that are able to preferentially label a specific ingredient or component in a sample enable the researcher to determine the presence, quantity and/or location of that specific ingredient or component. In addition, specific systems can be monitored with respect to their spatial and temporal distribution in diverse environments.

Fluorescence and colorimetric methods are extremely widespread in chemistry and biology. These methods give useful information on the presence, structure, distance, orientation, complexation and/or location for biomolecules. In addition, time-resolved methods are increasingly used in measurements of dynamics and kinetics. As a result, many strategies for fluorescence or color labeling of biomolecules, such as nucleic acids and protein, have been developed. Since analysis of biomolecules typically occurs in an aqueous environment, the focus has been on development and use of dyes compatible with aqueous systems that can elucidate desired spatial information and biomolecule interactions.

Accordingly, techniques involving resonance energy transfer have been developed to reveal such structural information. Specifically, Förster resonance energy transfer (“FRET”—sometimes also used interchangeably with fluorescence resonance energy transfer) techniques produce information that reliably measures change biomolecular distances and interactions. Resonance energy transfer techniques are relatively cheap and measurements can be obtained rapidly; however, FRET suffers from several limitations related to the orientation and positioning of chromophores as well as energy transfer masking due to free fluorophores and undesirable pH sensitivity.

There is thus a need in the art for water soluble dyes, especially resonance energy transfer dyes, having an increased molar brightness and/or increased FRET emission signal. Ideally, such dyes and biomarkers should be intensely colored or fluorescent and should be available in a variety of colors and fluorescent wavelengths. The present invention fulfills this need and provides further related advantages.

BRIEF SUMMARY

In brief, embodiments of the present invention are generally directed to compounds useful as water soluble, fluorescent and/or colored dyes and/or probes that enable visual detection of analyte molecules, such as biomolecules, as well as reagents for their preparation. In particular, in some embodiments, the compounds of this disclosure are useful because they enable FRET fluorescence emission associated with the same. Methods for visually detecting analyte molecules using the dyes are also described.

Embodiments of the presently disclosed dyes include two or more fluorescent and/or colored moieties (i.e., chromophores) covalently linked by a linker (“L⁴”). In contrast to previous reports of dimeric and/or polymeric dyes, the present dyes are significantly brighter than the corresponding monomeric dye compound and enable FRET absorbance and emission as a result of intramolecular interactions. While, not wishing to be bound by theory, it is believed that particular linkers provide sufficient proximity between the fluorescent and/or colored moieties such that intramolecular FRET is optimized.

The water soluble, fluorescent or colored dyes of embodiments of the invention are intensely colored, enable FRET processes (e.g., absorbance, emission, Stokes shifts) and/or fluorescent and can be readily observed by visual inspection or other means. In some embodiments the compounds may be observed without prior illumination or chemical or enzymatic activation. By appropriate selection of the dye, as described herein, visually detectable analyte molecules of a variety of colors may be obtained as well as valuable spatial information about target molecules.

In one embodiment, compounds having the following structure (I) are provided:

or a stereoisomer, tautomer or salt thereof, wherein R¹, R², R³, R⁴, R⁵, L¹, L², L³, L⁴, M¹, M², m and n are as defined herein.

Another embodiment provides a compound having the following structure (II):

or a stereoisomer, salt or tautomer thereof, wherein R¹, R², R³, R⁴, R⁵, L¹, L², L³, L⁴, M¹, M², m and n are as defined herein.

Yet another embodiment provides a polymer compound comprising an acceptor chromophore having an acceptor transition dipole moment and being covalently linked to a polymer backbone, and a donor chromophore having a donor transition dipole moment and being covalently linked to the polymer backbone, wherein the polymer compound adopts a confirmation in solution at physiological conditions wherein the effective distance between the acceptor chromophore and the donor chromophore is less than about 50.0 nm and the acceptor transition dipole and the donor transition dipole are substantially parallel.

The foregoing embodiments describe compounds that find utility in a number of applications, including use as FRET dyes, fluorescent and/or colored dyes in various analytical methods.

In another embodiment, a method for staining a sample is provided, the method comprises adding to said sample one of the foregoing compounds in an amount sufficient to produce an optical response when said sample is illuminated at an appropriate wavelength.

In still other embodiments, the present disclosure provides a method for visually detecting an analyte molecule, comprising:

(a) providing one of the foregoing compounds (e.g., a compound of structure (I) or structure (II)); and

(b) detecting the compound by its visible properties.

Other disclosed methods include a method for visually detecting a biomolecule, the method comprising:

(a) ad-mixing one of the foregoing compounds (e.g., a compound of structure (I) or structure (II)) with one or more biomolecules; and

(b) detecting the compound by its visible properties.

Other embodiments are directed to a composition comprising at least one of the foregoing compounds (e.g., a compound of structure (I) or structure (II)) and one or more biomolecules. Use of such compositions in analytical methods for detection of the one or more analyte (e.g., biomolecules) is also provided.

These and other aspects of the invention will be apparent upon reference to the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, identical reference numbers identify similar elements. The sizes and relative positions of elements in the figures are not necessarily drawn to scale and some of these elements are enlarged and positioned to improve figure legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the figures.

FIG. 1 shows the emission spectra of Compounds I-1 through I-4, each having various spacer lengths between pendant boron-dipyrromethene (“BODIPY”) and fluorescein-based chromophores.

FIG. 2 illustrates the emission spectra of Compounds I-5 through I-8, each having various spacer lengths between pendant Texas Red and fluorescein-based chromophores.

FIG. 3 depicts the emission spectra of Compounds I-9 through I-12 to compare donor emission for representative polymer dye compounds.

FIG. 4 shows emission spectra of Compounds I-13 through I-19 to compare how changes in the polymer compound affect emission.

FIG. 5 shows the emission spectra for Compounds I-20 through I-23 and the effect of spacer length on the same.

FIG. 6 depicts the absorbance spectrum of Compound 1-24, which has 3 distinct dye moieties pendant to the polymer backbone

FIG. 7 displays emission spectra for Compound 1-24 for pH values of 7.0 and 9.0.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details.

Unless the context requires otherwise, throughout the present specification and claims, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to”.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

“Amino” refers to the —NH₂ group.

“Carboxy” refers to the —CO₂H group.

“Cyano” refers to the —CN group.

“Formyl” refers to the —C(═O)H group.

“Hydroxy” or “hydroxyl” refers to the —OH group.

“Imino” refers to the ═NH group.

“Nitro” refers to the —NO₂ group.

“Oxo” refers to the ═O substituent group.

“Sulfhydryl” refers to the —SH group.

“Thioxo” refers to the ═S group.

“Alkyl” refers to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, containing no unsaturation, having from one to twelve carbon atoms (C₁-C₁₂ alkyl), one to eight carbon atoms (C₁-C₈ alkyl) or one to six carbon atoms (C₁-C₆ alkyl), and which is attached to the rest of the molecule by a single bond, e.g., methyl, ethyl, n-propyl, 1-methylethyl (iso-propyl), n-butyl, n-pentyl, 1,1-dimethylethyl (t-butyl), 3-methylhexyl, 2-methylhexyl, and the like. Unless stated otherwise specifically in the specification, alkyl groups are optionally substituted. “Alkylene” or “alkylene chain” refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing no unsaturation, and having from one to twelve carbon atoms, e.g., methylene, ethylene, propylene, n-butylene, ethenylene, propenylene, n-butenylene, propynylene, n-butynylene, and the like. The alkylene chain is attached to the rest of the molecule through a single bond and to the radical group through a single bond. The points of attachment of the alkylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, alkylene is optionally substituted.

“Alkenylene” or “alkenylene chain” refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing at least one carbon-carbon double bond and having from two to twelve carbon atoms, e.g., ethenylene, propenylene, n-butenylene, and the like. The alkenylene chain is attached to the rest of the molecule through a single bond and to the radical group through a double bond or a single bond. The points of attachment of the alkenylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, alkenylene is optionally substituted.

“Alkynylene” or “alkynylene chain” refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing at least one carbon-carbon triple bond and having from two to twelve carbon atoms, e.g., ethenylene, propenylene, n-butenylene, and the like. The alkynylene chain is attached to the rest of the molecule through a single bond and to the radical group through a double bond or a single bond. The points of attachment of the alkynylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, alkynylene is optionally substituted.

“Alkylether” refers to any alkyl group as defined above, wherein at least one carbon-carbon bond is replaced with a carbon-oxygen bond. The carbon-oxygen bond may be on the terminal end (as in an alkoxy group) or the carbon oxygen bond may be internal (i.e., C—O—C). Alkylethers include at least one carbon oxygen bond, but may include more than one. For example, polyethylene glycol (PEG) is included within the meaning of alkylether. Unless stated otherwise specifically in the specification, an alkylether group is optionally substituted. For example, in some embodiments an alkylether is substituted with an alcohol or —OP(═R_(a))(R_(b))R_(c), wherein each of R_(a), R_(b) and R_(c) is as defined for compounds of structure (I).

“Alkoxy” refers to a group of the formula —OR_(a) where R_(a) is an alkyl group as defined above containing one to twelve carbon atoms. Unless stated otherwise specifically in the specification, an alkoxy group is optionally substituted.

“Heteroalkylene” refers to an alkylene group, as defined above, comprising at least one heteroatom (e.g., N, O, P or S) within the alkylene chain or at a terminus of the alkylene chain. In some embodiments, the heteroatom is within the alkylene chain (i.e., the heteroalkylene comprises at least one carbon-[heteroatom]-carbon bond, where x is 1, 2 or 3). In other embodiments, the heteroatom is at a terminus of the alkylene and thus serves to join the alkylene to the remainder of the molecule (e.g., M1-H-A-M2, where M1 and M2 are portions of the molecule, H is a heteroatom and A is an alkylene). Unless stated otherwise specifically in the specification, a heteroalkylene group is optionally substituted. Exemplary heteroalkylene groups include ethylene oxide (e.g., polyethylene oxide) and the “C,” “HEG,” “TEG,” “PEG 1K” and variations thereof, linking groups illustrated below:

Multimers of the above C-linker, HEG linker and/or PEG 1K linker are included in various embodiments of heteroalkylene linkers.

In some embodiments, vIn some embodiments of the PEG 1K linker, n is 25. Multimers may comprise, for example, the following structure:

wherein x is 0 or an integer greater than 0, for example, x ranges from 0-100 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10).

“Heteroalkenylene” is a heteroalkylene, as defined above, comprising at least one carbon-carbon double bond. Unless stated otherwise specifically in the specification, a heteroalkenylene group is optionally substituted.

“Heteroalkynylene” is a heteroalkylene comprising at least one carbon-carbon triple bond. Unless stated otherwise specifically in the specification, a heteroalkynylene group is optionally substituted.

“Heteroatomic” in reference to a “heteroatomic linker” refers to a linker group consisting of one or more heteroatom. Exemplary heteroatomic linkers include single atoms selected from the group consisting of O, N, P and S, and multiple heteroatoms for example a linker having the formula —P(O⁻)(═O)O— or —OP(O⁻)(═O)O— and multimers and combinations thereof.

“Phosphate” refers to the —OP(═O)(R_(a))R_(b) group, wherein R_(a) is OH, O⁻ or OR_(c); and R_(b) is OH, O⁻, OR_(c), a thiophosphate group or a further phosphate group, wherein R_(c) is a counter ion (e.g., Na+ and the like).

“Phosphoalkyl” refers to the —OP(═O)(R_(a))R_(b) group, wherein R_(a) is OH, O⁻ or OR_(c); and R_(b) is —O alkyl, wherein R_(c) is a counter ion (e.g., Na⁺ and the like). Unless stated otherwise specifically in the specification, a phosphoalkyl group is optionally substituted. For example, in certain embodiments, the —O alkyl moiety in a phosphoalkyl group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether.

“Phosphoalkylether” refers to the —OP(═O)(R_(a))R_(b) group, wherein R_(a) is OH, O⁻ or OR_(c); and R_(b) is —O alkylether, wherein R_(c) is a counter ion (e.g., Na⁺ and the like). Unless stated otherwise specifically in the specification, a phosphoalkylether group is optionally substituted. For example, in certain embodiments, the —O alkylether moiety in a phosphoalkylether group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether.

“Thiophosphate” refers to the —OP(═R_(a))(R_(b))R_(c) group, wherein R_(a) is O or S, R_(b) is OH, O⁻, S⁻, OR_(d) or SR_(d); and R_(c) is OH, SH, O⁻, S⁻, OR_(d), SR_(d), a phosphate group or a further thiophosphate group, wherein R_(d) is a counter ion (e.g., Na⁺ and the like) and provided that: i) R_(a) is S; ii) R_(b) is S⁻ or SR_(d); iii) R_(c) is SH, S⁻ or SR_(d); or iv) a combination of i), ii) and/or iii).

“Thiophosphoalkyl” refers to the —OP(═R_(a))(R_(b))R_(c) group, wherein R_(a) is O or S, R_(b) is OH, O⁻, S⁻, OR_(d) or SR_(d); and R_(c) is —O alkyl, wherein R_(d) is a counter ion (e.g., Na+ and the like) and provided that: i) R_(a) is S; ii) R_(b) is S⁻ or SR_(d); or iii)R_(a) is S and R_(b) is S⁻ or SR_(d). Unless stated otherwise specifically in the specification, a thiophosphoalkyl group is optionally substituted. For example, in certain embodiments, the —O alkyl moiety in a thiophosphoalkyl group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether.

“Thiophosphoalkylether” refers to the —OP(═R_(a))(R_(b))R_(c) group, wherein R_(a) is O or S, R_(b) is OH, O⁻, S⁻, OR_(d) or SR_(d); and R_(c) is —O alkylether, wherein R_(d) is a counter ion (e.g., Na⁺ and the like) and provided that: i) R_(a) is S; ii) R_(b) is S⁻ or SR_(d); or iii)R_(a) is S and R_(b) is S⁻ or SR_(d). Unless stated otherwise specifically in the specification, a thiophosphoalkylether group is optionally substituted. For example, in certain embodiments, the —O alkylether moiety in a thiophosphoalkyl group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether.

“Carbocyclic” refers to a stable 3- to 18-membered aromatic or non-aromatic ring comprising 3 to 18 carbon atoms. Unless stated otherwise specifically in the specification, a carbocyclic ring may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems, and may be partially or fully saturated. Non-aromatic carbocyclyl radicals include cycloalkyl, while aromatic carbocyclyl radicals include aryl. Unless stated otherwise specifically in the specification, a carbocyclic group is optionally substituted.

“Cycloalkyl” refers to a stable non-aromatic monocyclic or polycyclic carbocyclic ring, which may include fused or bridged ring systems, having from three to fifteen carbon atoms, preferably having from three to ten carbon atoms, and which is saturated or unsaturated and attached to the rest of the molecule by a single bond. Monocyclic cyclocalkyls include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptly, and cyclooctyl. Polycyclic cycloalkyls include, for example, adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo-[2.2.1]heptanyl, and the like. Unless stated otherwise specifically in the specification, a cycloalkyl group is optionally substituted.

“Aryl” refers to a ring system comprising at least one carbocyclic aromatic ring. In some embodiments, an aryl comprises from 6 to 18 carbon atoms. The aryl ring may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems. Aryls include, but are not limited to, aryls derived from aceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene, benzene, chrysene, fluoranthene, fluorene, as-indacene, s-indacene, indane, indene, naphthalene, phenalene, phenanthrene, pleiadene, pyrene, and triphenylene. Unless stated otherwise specifically in the specification, an aryl group is optionally substituted.

“Heterocyclic” refers to a stable 3- to 18-membered aromatic or non-aromatic ring comprising one to twelve carbon atoms and from one to six heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur. Unless stated otherwise specifically in the specification, the heterocyclic ring may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems; and the nitrogen, carbon or sulfur atoms in the heterocyclic ring may be optionally oxidized; the nitrogen atom may be optionally quaternized; and the heterocyclic ring may be partially or fully saturated. Examples of aromatic heterocyclic rings are listed below in the definition of heteroaryls (i.e., heteroaryl being a subset of heterocyclic). Examples of non-aromatic heterocyclic rings include, but are not limited to, dioxolanyl, thienyl[1,3]dithianyl, decahydroisoquinolyl, imidazolinyl, imidazolidinyl, isothiazolidinyl, isoxazolidinyl, morpholinyl, octahydroindolyl, octahydroisoindolyl, 2-oxopiperazinyl, 2-oxopiperidinyl, 2-oxopyrrolidinyl, oxazolidinyl, piperidinyl, piperazinyl, 4-piperidonyl, pyrrolidinyl, pyrazolidinyl, pyrazolopyrimidinyl, quinuclidinyl, thiazolidinyl, tetrahydrofuryl, trioxanyl, trithianyl, triazinanyl, tetrahydropyranyl, thiomorpholinyl, thiamorpholinyl, 1-oxo-thiomorpholinyl, and 1,1-dioxo-thiomorpholinyl. Unless stated otherwise specifically in the specification, a heterocyclic group is optionally substituted.

“Heteroaryl” refers to a 5- to 14-membered ring system comprising one to thirteen carbon atoms, one to six heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur, and at least one aromatic ring. For purposes of certain embodiments of this invention, the heteroaryl radical may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems; and the nitrogen, carbon or sulfur atoms in the heteroaryl radical may be optionally oxidized; the nitrogen atom may be optionally quaternized. Examples include, but are not limited to, azepinyl, acridinyl, benzimidazolyl, benzthiazolyl, benzindolyl, benzodioxolyl, benzofuranyl, benzooxazolyl, benzothiazolyl, benzothiadiazolyl, benzo[b][1,4]dioxepinyl, 1,4-benzodioxanyl, benzonaphthofuranyl, benzoxazolyl, benzodioxolyl, benzodioxinyl, benzopyranyl, benzopyranonyl, benzofuranyl, benzofuranonyl, benzothienyl (benzothiophenyl), benzotriazolyl, benzo[4,6]imidazo[1,2-a]pyridinyl, benzoxazolinonyl, benzimidazolthionyl, carbazolyl, cinnolinyl, dibenzofuranyl, dibenzothiophenyl, furanyl, furanonyl, isothiazolyl, imidazolyl, indazolyl, indolyl, indazolyl, isoindolyl, indolinyl, isoindolinyl, isoquinolyl, indolizinyl, isoxazolyl, naphthyridinyl, oxadiazolyl, 2-oxoazepinyl, oxazolyl, oxiranyl, 1-oxidopyridinyl, 1-oxidopyrimidinyl, 1-oxidopyrazinyl, 1-oxidopyridazinyl, 1-phenyl-1H-pyrrolyl, phenazinyl, phenothiazinyl, phenoxazinyl, phthalazinyl, pteridinyl, pteridinonyl, purinyl, pyrrolyl, pyrazolyl, pyridinyl, pyridinonyl, pyrazinyl, pyrimidinyl, pryrimidinonyl, pyridazinyl, pyrrolyl, pyrido[2,3-d]pyrimidinonyl, quinazolinyl, quinazolinonyl, quinoxalinyl, quinoxalinonyl, quinolinyl, isoquinolinyl, tetrahydroquinolinyl, thiazolyl, thiadiazolyl, thieno[3,2-d]pyrimidin-4-onyl, thieno[2,3-d]pyrimidin-4-onyl, triazolyl, tetrazolyl, triazinyl, and thiophenyl (i.e. thienyl). Unless stated otherwise specifically in the specification, a heteroaryl group is optionally substituted.

The suffix “-ene” refers to a particular structural feature (e.g., alkyl, aryl, heteroalkyl) attached to the rest of the molecule through a single bond and to the radical group through a single bond. In other words, the suffix “-ene” refers to a particular structural feature having the description given herein which is a linker between the molecule and a radical group. The points of attachment of the “-ene” chain to the rest of the molecule and to the radical group can be through one atom of or any two atoms within the chain. For example, an alkyleneheteroalkylene refers to a linker comprising a alkylene portion and a heteroalkylene portion.

“Fused” refers to a ring system comprising at least two rings, wherein the two rings share at least one common ring atom, for example two common ring atoms. When the fused ring is a heterocyclyl ring or a heteroaryl ring, the common ring atom(s) may be carbon or nitrogen. Fused rings include bicyclic, tricyclic, tertracyclic, and the like.

“Conjugation” refers to the overlap of one p-orbital with another p-orbital across an intervening sigma bond. Conjugation may occur in cyclic or acyclic compounds. A “degree of conjugation” refers to the overlap of at least one p-orbital with another p-orbital across an intervening sigma bond. For example, 1,3-butadine has one degree of conjugation, while benzene and other aromatic compounds typically have multiple degrees of conjugation. Fluorescent and colored compounds typically comprise at least one degree of conjugation.

“Fluorescent” refers to a molecule which is capable of absorbing light of a particular frequency and emitting light of a different frequency. Fluorescence is well-known to those of ordinary skill in the art.

“Colored” refers to a molecule which absorbs light within the colored spectrum (i.e., red, yellow, blue and the like).

“FRET” refers to Förster resonance energy transfer refers to a physical interaction whereby energy from the excitation of one moiety (e.g., a first chromophore or “donor”) is transferred to an adjacent moiety (e.g., a second chromophore or “acceptor”). “FRET” is sometimes also used interchangeably with fluorescence resonance energy transfer (i.e., when each chromophore is a fluorescent moiety). Generally, FRET requires that (1) the excitation or absorption spectrum of the acceptor chromophore overlaps with the emission spectrum of the donor chromophore; (2) the transition dipole moments of the acceptor and donor chromophores are substantially parallel (i.e., at about 0° or 180°; and (3) the acceptor and donor chromophores share a spatial proximity (i.e., close to each other). The transfer of energy from the donor to the acceptor occurs through non-radiative dipole-dipole coupling and the distance between the donor chromophore and acceptor chromophore is generally much less than the wavelength(s) of light.

“Donor” or “donor chromophore” refers to a chromophore (e.g., a fluorophore) that is or can be induced into an excited electronic state and may transfer its excitation energy to a nearby acceptor chromophore in a non-radiative fashion through long-range dipole-dipole interactions. Without wishing to be bound by theory, it is thought that the energy transfer occurs because the oscillating dipoles of the respective chromophores have similar resonance frequencies. A donor and acceptor that have these similar resonance frequencies are referred to as a “donor-acceptor pair(s),” which is used interchangeably with “FRET moieties” or “FRET dyes.”

“Acceptor” or “acceptor chromophore” refers to a chromophore (e.g., a fluorophore) to which excitation energy from a donor chromophore is transferred via a non-radiative transfer through long-range dipole-dipole interaction.

“Stoke's shift” refers to a difference between positions (e.g., wavelengths) of the band maxima of absorption and emission spectra of an electronic transition (e.g., from excited state to non-excited state, or vice versa). In some embodiments, the compounds have a Stoke's shift greater than 25 nm, greater than 30 nm, greater than 35 nm, greater than 40 nm, greater than 45 nm, greater than 50 nm, greater than 55 nm, greater than 60 nm, greater than 65 nm, greater than 70 nm, greater than 75 nm, greater than 80 nm, greater than 85 nm, greater than 90 nm, greater than 95 nm, greater than 100 nm, greater than 110 nm, greater than 120 nm, greater than 130 nm, greater than 140 nm, greater than 150 nm, greater than 160 nm, greater than 170 nm, greater than 180 nm, greater than 190 nm, or greater than 200 nm.

A “linker” refers to a contiguous chain of at least one atom, such as carbon, oxygen, nitrogen, sulfur, phosphorous and combinations thereof, which connects a portion of a molecule to another portion of the same molecule or to a different molecule, moiety or solid support (e.g., microparticle). Linkers may connect the molecule via a covalent bond or other means, such as ionic or hydrogen bond interactions.

“Physiological conditions” refers to a solution or medium having a temperature ranging from about 20 to 40° C., an atmospheric pressure of about 1 atm (101 kPa or 14.7 psi), a pH of about 6 to 8, a glucose concentration of about 1 to 20 mM, atmospheric oxygen concentration, and/or earth gravity. “Physiological conditions” includes a solution or medium having a subset of these properties (e.g., having a temperature ranging from 20 to 40° C. and a pH of about 6 to 8). Such conditions may also include buffer components or systems including, but not limited to phosphate, bicarbonate, hemoglobin and/or protein.

The term “biomolecule” refers to any of a variety of biological materials, including nucleic acids, carbohydrates, amino acids, polypeptides, glycoproteins, hormones, aptamers and mixtures thereof.

More specifically, the term is intended to include, without limitation, RNA,

DNA, oligonucleotides, modified or derivatized nucleotides, enzymes, receptors, prions, receptor ligands (including hormones), antibodies, antigens, and toxins, as well as bacteria, viruses, blood cells, and tissue cells. The visually detectable biomolecules of the invention (e.g., compounds of structures (I) or (II) having a biomolecule linked thereto) are prepared, as further described herein, by contacting a biomolecule with a compound having a reactive group that enables attachment of the biomolecule to the compound via any available atom or functional group, such as an amino, hydroxy, carboxyl, or sulfhydryl group on the biomolecule.

A “reactive group” is a moiety capable of reacting with a second reactive group (e.g., a “complementary reactive group”) to form one or more covalent bonds, for example by a displacement, oxidation, reduction, addition or cycloaddition reaction. Exemplary reactive groups are provided in Table 1, and include for example, nucleophiles, electrophiles, dienes, dienophiles, aldehyde, oxime, hydrazone, alkyne, amine, azide, acylazide, acylhalide, nitrile, nitrone, sulfhydryl, disulfide, sulfonyl halide, isothiocyanate, imidoester, activated ester, ketone, α,β-unsaturated carbonyl, alkene, maleimide, α-haloimide, epoxide, aziridine, tetrazine, tetrazole, phosphine, biotin, thiirane and the like.

“Bio-conjugation” or “bio-conjugate” and related variations refer to a chemical reaction strategy for forming a stable covalent bond between two molecules. The term “bio-conjugation” is generally used when one of the molecules is a biomolecule (e.g., an antibody), but can be used to describe forming a covalent bond with a non-biomolecule (e.g., a polymeric resin). The product or compound resulting from such a reaction strategy is a “conjugate,” “bio-conjugate” or a grammatical equivalent.

The terms “visible” and “visually detectable” are used herein to refer to substances that are observable by visual inspection, without prior illumination, or chemical or enzymatic activation. Such visually detectable substances absorb and emit light in a region of the spectrum ranging from about 300 to about 900 nm. Preferably, such substances are intensely colored, preferably having a molar extinction coefficient of at least about 40,000, more preferably at least about 50,000, still more preferably at least about 60,000, yet still more preferably at least about 70,000, and most preferably at least about 80,000 M⁻¹ cm⁻¹. The compounds of the invention may be detected by observation with the naked eye, or with the aid of an optically based detection device, including, without limitation, absorption spectrophotometers, transmission light microscopes, digital cameras and scanners. Visually detectable substances are not limited to those which emit and/or absorb light in the visible spectrum. Substances which emit and/or absorb light in the ultraviolet (UV) region (about 10 nm to about 400 nm), infrared (IR) region (about 700 nm to about 1 mm), and substances emitting and/or absorbing in other regions of the electromagnetic spectrum are also included with the scope of “visually detectable” substances.

For purposes of embodiments of the invention, the term “photostable visible dye” refers to a chemical moiety that is visually detectable, as defined hereinabove, and is not significantly altered or decomposed upon exposure to light. Preferably, the photostable visible dye does not exhibit significant bleaching or decomposition after being exposed to light for at least one hour. More preferably, the visible dye is stable after exposure to light for at least 12 hours, still more preferably at least 24 hours, still yet more preferably at least one week, and most preferably at least one month. Non-limiting examples of photostable visible dyes suitable for use in the compounds and methods of the invention include azo dyes, thioindigo dyes, quinacridone pigments, dioxazine, phthalocyanine, perinone, diketopyrrolopyrrole, quinophthalone, and truarycarbonium.

As used herein, the term “perylene derivative” is intended to include any substituted perylene that is visually detectable. However, the term is not intended to include perylene itself. The terms “anthracene derivative”, “naphthalene derivative”, and “pyrene derivative” are used analogously. In some preferred embodiments, a derivative (e.g., perylene, pyrene, anthracene or naphthalene derivative) is an imide, bisimide or hydrazamimide derivative of perylene, anthracene, naphthalene, or pyrene.

The polymer compounds of various embodiments of the invention are useful for a wide variety of analytical applications, such as biochemical and biomedical applications, in which there is a need to determine the presence, location, spatial interaction or quantity of a particular analyte (e.g., biomolecule). In another aspect, therefore, the invention provides a method for visually detecting a biomolecule, comprising: (a) providing a biological system with a visually detectable biomolecule comprising the compound of the embodiments disclosed herein (e.g., structure (I) or structure (II)) linked to a biomolecule; and (b) detecting the biomolecule by its visible properties. For purposes of the invention, the phrase “detecting the biomolecule by its visible properties” means that the biomolecule, without illumination or chemical or enzymatic activation, is observed with the naked eye, or with the aid of a optically based detection device, including, without limitation, absorption spectrophotometers, transmission light microscopes, digital cameras and scanners. A densitometer may be used to quantify the amount of visually detectable biomolecule present. For example, the relative quantity of the biomolecule in two samples can be determined by measuring relative optical density. If the stoichiometry of dye molecules per biomolecule is known, and the extinction coefficient of the dye molecule is known, then the absolute concentration of the biomolecule can also be determined from a measurement of optical density. As used herein, the term “biological system” is used to refer to any solution or mixture comprising one or more biomolecules in addition to the visually detectable biomolecule. Non-limiting examples of such biological systems include cells, cell extracts, tissue samples, electrophoretic gels, assay mixtures, and hybridization reaction mixtures.

“Solid support” or “solid support residue” refers to any solid substrate known in the art for solid-phase support of molecules, for example a “microparticle” refers to any of a number of small particles useful for attachment to compounds of the invention, including, but not limited to, glass beads, magnetic beads, polymeric beads, non-polymeric beads, and the like. In certain embodiments, a microparticle comprises polystyrene beads.

“Base pairing moiety” refers to a heterocyclic moiety capable of hybridizing with a complementary heterocyclic moiety via hydrogen bonds (e.g., Watson-Crick base pairing). Base pairing moieties include natural and unnatural bases. Non-limiting examples of base pairing moieties are RNA and DNA bases such adenosine, guanosine, thymidine, cytosine and uridine and analogues thereof.

Embodiments of the invention disclosed herein are also meant to encompass all compounds of structure (I) or (II) being isotopically-labelled by having one or more atoms replaced by an atom having a different atomic mass or mass number. Examples of isotopes that can be incorporated into the disclosed compounds include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorous, fluorine, chlorine, and iodine, such as ²H, ³H, ¹¹C, ¹³C, ¹⁴C, ¹³N, ¹⁵N, ¹⁵O, ¹⁷O, ¹⁸O, ³¹P, ³²P, ³⁵S, ¹⁸F, ³⁶Cl, ¹²³I, and ¹²⁵I, respectively.

Isotopically-labeled compounds of structure (I) or (II) can generally be prepared by conventional techniques known to those skilled in the art or by processes analogous to those described below and in the following Examples using an appropriate isotopically-labeled reagent in place of the non-labeled reagent previously employed.

“Stable compound” and “stable structure” are meant to indicate a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into an efficacious therapeutic agent.

“Optional” or “optionally” means that the subsequently described event or circumstances may or may not occur; such a description includes instances where the event or circumstance occurs and instances where it does not. For example, “optionally substituted alkyl” means that the alkyl group may or may not be substituted and that the description includes both substituted alkyl groups and alkyl groups having no substitution.

“Salt” includes both acid and base addition salts.

“Acid addition salt” refers to those salts which are formed with inorganic acids such as, but not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as, but not limited to, acetic acid, 2,2-dichloroacetic acid, adipic acid, alginic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, 4-acetamidobenzoic acid, camphoric acid, camphor-10-sulfonic acid, capric acid, caproic acid, caprylic acid, carbonic acid, cinnamic acid, citric acid, cyclamic acid, dodecylsulfuric acid, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, formic acid, fumaric acid, galactaric acid, gentisic acid, glucoheptonic acid, gluconic acid, glucuronic acid, glutamic acid, glutaric acid, 2-oxo-glutaric acid, glycerophosphoric acid, glycolic acid, hippuric acid, isobutyric acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, mucic acid, naphthalene-1,5-disulfonic acid, naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, pamoic acid, propionic acid, pyroglutamic acid, pyruvic acid, salicylic acid, 4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid, tartaric acid, thiocyanic acid, p-toluenesulfonic acid, trifluoroacetic acid, undecylenic acid, and the like.

“Base addition salt” refers to those salts which are prepared from addition of an inorganic base or an organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as ammonia, isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, diethanolamine, ethanolamine, deanol, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, benethamine, benzathine, ethylenediamine, glucosamine, methylglucamine, theobromine, triethanolamine, tromethamine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins and the like. Particularly preferred organic bases are isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline and caffeine.

Crystallizations may produce a solvate of the compounds described herein. Embodiments of the present invention include all solvates of the described compounds. As used herein, the term “solvate” refers to an aggregate that comprises one or more molecules of a compound of the invention with one or more molecules of solvent. The solvent may be water, in which case the solvate may be a hydrate. Alternatively, the solvent may be an organic solvent. Thus, the compounds of the present invention may exist as a hydrate, including a monohydrate, dihydrate, hemihydrate, sesquihydrate, trihydrate, tetrahydrate and the like, as well as the corresponding solvated forms. The compounds of the invention may be true solvates, while in other cases the compounds of the invention may merely retain adventitious water or another solvent or be a mixture of water plus some adventitious solvent.

Embodiments of the compounds of the invention (e.g., compounds of structure I or II), or their salts, tautomers or solvates may contain one or more stereocenters and may thus give rise to enantiomers, diastereomers, and other stereoisomeric forms that may be defined, in terms of absolute stereochemistry, as (R)− or (S)− or, as (D)− or (L)− for amino acids. Embodiments of the present invention are meant to include all such possible isomers, as well as their racemic and optically pure forms. Optically active (+) and (−), (R)− and (S)−, or (D)− and (L)− isomers may be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques, for example, chromatography and fractional crystallization. Conventional techniques for the preparation/isolation of individual enantiomers include chiral synthesis from a suitable optically pure precursor or resolution of the racemate (or the racemate of a salt or derivative) using, for example, chiral high pressure liquid chromatography (HPLC). When the compounds described herein contain olefinic double bonds or other centers of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers. Likewise, all tautomeric forms are also intended to be included.

A “stereoisomer” refers to a compound made up of the same atoms bonded by the same bonds but having different three-dimensional structures, which are not interchangeable. The present invention contemplates various stereoisomers and mixtures thereof and includes “enantiomers”, which refers to two stereoisomers whose molecules are non-superimposable mirror images of one another.

A “tautomer” refers to a proton shift from one atom of a molecule to another atom of the same molecule. The present invention includes tautomers of any said compounds. Various tautomeric forms of the compounds are easily derivable by those of ordinary skill in the art.

The chemical naming protocol and structure diagrams used herein are a modified form of the I.U.P.A.C. nomenclature system, using the ACD/Name Version 9.07 software program and/or ChemDraw Ultra Version 11.0 software naming program (CambridgeSoft). Common names familiar to one of ordinary skill in the art are also used.

As noted above, in one embodiment of the present invention, compounds useful as FRET, fluorescent and/or colored dyes in various analytical methods are provided. In other embodiments, compounds useful as synthetic intermediates for preparation of compounds useful as FRET, fluorescent and/or colored dyes are provided. In general terms, embodiments of the present invention are directed to dimers and higher polymers of FRET, fluorescent and/or colored moieties. The FRET, fluorescent and/or colored moieties are linked by a linking moiety. Without wishing to be bound by theory, it is believed the linker helps to maintain sufficient spatial distance/proximity between the donor-acceptor pair(s) such that intramolecular quenching is reduced or eliminated, while maintain sufficient proximity to facilitate the non-radiative transfer of energy.

Accordingly, in some embodiments the compounds have the following structure (A):

wherein L is a linker sufficient to maintain spatial separation between one or more (e.g., each) M group so that intramolecular quenching is reduced or eliminated, and R¹, R², R³, L¹, L², L³ and n are as defined for structure (I) or structure (II).

In other embodiments is provided a compound having the following structure (I):

or a stereoisomer, salt or tautomer thereof, wherein:

M¹ and M² are, at each occurrence, independently a chromophore, provided that at least one occurrence of M¹ and M² combine to form a FRET donor-acceptor pair;

L¹ is, at each occurrence, an optional linker;

L² and L³ are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;

L⁴ is, at each occurrence, independently an alkylene or heteroalkylene linker;

R¹ is, at each occurrence, independently H, alkyl or alkoxy;

R² and R³ are each independently H, OH, SH, alkyl, alkoxy, alkylether, heteroalkyl, —OP(═R_(a))(R_(b))R_(c), Q, or a protected form thereof, or L′;

R⁴ is, at each occurrence, independently OH, SH, O⁻, S⁻, OR_(d) or SR_(d);

R⁵ is, at each occurrence, independently oxo, thioxo or absent;

R_(a) is O or S;

R_(b) is OH, SH, O⁻, S⁻, OR_(d) or SR_(d);

R_(c) is OH, SH, O⁻, S⁻, OR_(d), OL′, SR_(d), alkyl, alkoxy, heteroalkyl, heteroalkoxy, alkylether, alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether;

R_(d) is a counter ion;

Q is, at each occurrence, independently a moiety comprising a reactive group, or protected form thereof, capable of forming a covalent bond with an analyte molecule, a targeting moiety, a solid support or a complementary reactive group Q;

L′ is, at each occurrence, independently a linker comprising a covalent bond to Q, a linker comprising a covalent bond to a targeting moiety, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support, a linker comprising a covalent bond to a solid support residue, a linker comprising a covalent bond to a nucleoside or a linker comprising a covalent bond to a further compound of structure (I);

m is, at each occurrence, independently an integer of zero or greater; and

n is an integer of one or greater.

In some embodiments, at least one occurrence of L⁴ is heteroalkylene. In more specific embodiments, the heteroalkylene comprises alkylene oxide. In some related embodiments, the heteroalkylene comprises ethylene oxide.

In embodiments, at least one occurrence of L⁴ is alkylene. In some more specific embodiments, at least one alkylene is ethylene. In some embodiments, the alkylene is ethylene at each occurrence.

In some embodiments, L¹ is, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker. In some embodiments, L⁴ is a linker comprising a functional group capable of formation by reaction of two complementary reactive groups (e.g., an azide and an alkyne). In some embodiments, L⁴ is, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, alkyleneheteroarylenealkylene, alkyleneheterocyclylenealkylene, alkylenecarbocyclylenealkylene, heteroalkyleneheteroarylenealkylene, heteroalkyleneheterocyclylenealkylene, heteroalkylenecarbocyclylenealkylene, heteroalkyleneheteroaryleneheteroalkylene, heteroalkyleneheterocyclyleneheteroalkylene, heteroalkylenecarbocyclyleneheteroalkylene, alkyleneheteroaryleneheteroalkylene, alkyleneheterocyclyleneheteroalkylene, alkylenecarbocyclyleneheteroalkylene, heteroarylene, heterocyclylene, carbocyclylene, alkyleneheteroarylene, alkyleneheterocyclylene, heteroarylenealkylene, alkylenecarbocyclylene, carbocyclylenealkylene, heteroalkyleneheteroarylene, heteroalkyleneheterocyclylene, heteroaryleneheteroalkylene, heteroalkylenecarbocyclylene, carbocyclyleneheteroalkylene or heteroatomic linker. In some embodiments, L′ is optionally substituted.

In some embodiments, the compound has the following structure (IA):

wherein:

z is, at each occurrence, independently an integer from 1 to 100; and

m₁ and m₂ and m₃ are, at each occurrence, independently an integer from 0 to 6.

In some other embodiments, the compound has the following structure (IB):

wherein:

z is, at each occurrence, independently an integer from 1 to 100.

In a different embodiment, the compound has the following structure (IC):

wherein:

z is, at each occurrence, independently an integer from 1 to 100; and

x¹, x², x³ and x⁴ are, at each occurrence, independently an integer from 0 to 6.

In certain related embodiments, z is an integer from 3 to 6 at one or more occurrences. In some specific embodiments, x¹ and x³ are each 0 at each occurrence, and x² and x⁴ are each 1 at each occurrence. In some embodiments, x¹, x², x³ and x⁴ are each 1 at each occurrence. In one particular embodiment, L⁴ has the following structure:

wherein:

p is, at each occurrence, independently an integer from 0 to 6; and

y is, at each occurrence, independently an integer from 1 to 100.

In some embodiments, R³ comprises the following structure:

wherein:

p is, at each occurrence, independently an integer from 0 to 6; and

y is, at each occurrence, independently an integer from 1 to 100.

In certain embodiments, the compound has the following structure (ID):

In some related embodiments, the compound has the following structure (IE)

Another embodiment provides a compound having the following structure (II):

or a stereoisomer, salt or tautomer thereof, wherein:

M¹ and M² are, at each occurrence, independently a chromophore, provided that at least one occurrence of M¹ and M² combine to form a FRET acceptor-donor pair;

L¹ is at each occurrence, an optional linker;

L² and L³ are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;

L⁴ is, at each occurrence, independently an alkylene or heteroalkylene linker;

R¹ is, at each occurrence, independently H, alkyl or alkoxy;

R² and R³ are each independently H, OH, SH, alkyl, alkoxy, alkylether, heteroalkyl, —OP(═R_(a))(R_(b))R_(c), Q, or a protected form thereof, or L;

R⁴ is, at each occurrence, independently OH, SH, O⁻, S⁻, OR_(a) or SR_(d);

R⁵ is, at each occurrence, independently oxo, thioxo or absent;

R_(a) is O or S;

R_(b) is OH, SH, O⁻, S⁻, OR_(a) or SR_(d);

R_(c) is OH, SH, O⁻, S⁻, OR_(d), OL′, SR_(d), alkyl, alkoxy, heteroalkyl, heteroalkoxy, alkylether, alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether;

R_(d) is a counter ion;

Q is, at each occurrence, independently a moiety comprising a reactive group, or protected form thereof, capable of forming a covalent bond with an analyte molecule, a targeting moiety, a solid support or a complementary reactive group Q′;

L′ is, at each occurrence, independently a linker comprising a covalent bond to Q, a linker comprising a covalent bond to a targeting moiety, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support, a linker comprising a covalent bond to a solid support residue, a linker comprising a covalent bond to a nucleoside or a linker comprising a covalent bond to a further compound of structure (II);

m is, at each occurrence, independently an integer of zero to two or greater than 6; and

n is an integer of one or greater.

The various linkers and substituents (e.g., M¹, M², Q, R¹, R², R³, R^(c), L¹, L², L³, and L⁴) in the compound of structures (I) and (II) are optionally substituted with one more substituent. For example, in some embodiments the optional substituent is selected to optimize the water solubility or other property of the compounds of structures (I) or (II). In certain embodiments, each alkyl, alkoxy, alkylether, alkoxyalkylether, phosphoalkyl, thiophosphoalkyl, phosphoalkylether and thiophosphoalkylether in the compounds of structures (I) and (II) are optionally substituted with one more substituent selected from the group consisting of hydroxyl, alkoxy, alkylether, alkoxyalkylether, sulfhydryl, amino, alkylamino, carboxyl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether and thiophosphoalkylether.

The optional linker L¹ can be used as a point of attachment of the M¹ and M² moieties to the remainder of the compound. For example, in some embodiments a synthetic precursor to the compound of structure (I) or structure (II) is prepared, and the M¹ and/or M² moiety is attached to the synthetic precursor using any number of facile methods known in the art, for example methods referred to as “click chemistry.” For this purpose any reaction which is rapid and substantially irreversible can be used to attach M¹ or M² or both to the synthetic precursor to form a compound of structure (I) or structure (II). Exemplary reactions include the copper catalyzed reaction of an azide and alkyne to form a triazole (Huisgen 1, 3-dipolar cycloaddition), reaction of a diene and dienophile (Diels-Alder), strain-promoted alkyne-nitrone cycloaddition, reaction of a strained alkene with an azide, tetrazine or tetrazole, alkene and azide [3+2] cycloaddition, alkene and tetrazine inverse-demand Diels-Alder, alkene and tetrazole photoreaction and various displacement reactions, such as displacement of a leaving group by nucleophilic attack on an electrophilic atom. In some embodiments the reaction to form L¹ may be performed in an aqueous environment.

Accordingly, in some embodiments L^(i) is at each occurrence a linker comprising a functional group capable of formation by reaction of two complementary reactive groups, for example a functional group which is the product of one of the foregoing “click” reactions. In various embodiments, for at least one occurrence of L¹, the functional group can be formed by reaction of an aldehyde, oxime, hydrazone, alkyne, amine, azide, acylazide, acylhalide, nitrile, nitrone, sulfhydryl, disulfide, sulfonyl halide, isothiocyanate, imidoester, activated ester, ketone, α,β-unsaturated carbonyl, alkene, maleimide, α-haloimide, epoxide, aziridine, tetrazine, tetrazole, phosphine, biotin or thiirane functional group with a complementary reactive group.

In other embodiments, for at least one occurrence of L¹, the functional group can be formed by reaction of an alkyne and an azide.

In more embodiments, for at least one occurrence of L¹, the functional group comprises an alkene, ester, amide, thioester, disulfide, carbocyclic, heterocyclic or heteroaryl group. In some more specific embodiments, for at least one occurrence of L¹, L¹ is a linker comprising a triazolyl functional group.

In still other embodiments, for at least one occurrence of L¹, L¹-M has the following structure:

wherein L^(1a) and L^(1b) are each independently optional linkers.

In different embodiments, for at least one occurrence of L¹, L¹-M has the following structure:

wherein L^(1a) and L^(1b) are each independently optional linkers.

In various embodiments of the foregoing, L^(1a) or L^(1b), or both, is absent. In other embodiments, L^(1a) or L^(1b), or both, is present.

In some embodiments L^(1a) and L^(1b), when present, are each independently alkylene or heteroalkylene. For example, in some embodiments L^(1a) and L^(1b), when present, independently have one of the following structures:

In still other different embodiments, L¹ is at each occurrence, independently an optional alkylene or heteroalkylene linker.

In more embodiments, L² and L³ are, at each occurrence, independently C₁-C₆ alkylene, C₂-C₆ alkenylene or C₂-C₆ alkynylene.

In some embodiments, at least one occurrence of L¹ has one of the following structures:

wherein

a, b, and c are each independently an integer ranging from 1-6.

In some embodiments, each occurrence of L¹ has one of the following structures:

wherein

a, b, and c are each independently an integer ranging from 1-6.

In some embodiments, at least one occurrence of L¹ has one of the following structures:

In some embodiments, each occurrence of L¹ has one of the following structures:

In still other embodiments, R⁴ is, at each occurrence, independently OH, O⁻ or OR_(d). It is understood that “OR_(d)” and “SR_(d)” are intended to refer to O⁻ and S⁻ associated with a cation. For example, the disodium salt of a phosphate group may be represented as:

where R_(a) is sodium (Na⁺).

In other embodiments, R⁵ is, at each occurrence, oxo.

In some different embodiments of any of the foregoing compounds, R¹ is H.

In other various embodiments, R² and R³ are each independently OH or −OP(═R_(a))(R_(b))R_(c). In some different embodiments, R² or R³ is OH or —OP(═R_(a))(R_(b))R_(c), and the other of R² or R³ is Q or a linker comprising a covalent bond to Q. In some embodiments, R² and R³ are each independently —OP(═R_(a))(R_(b))R_(c). In some specific embodiments, R_(c) is OL′. In some of those embodiments, L′ is a heteroalkylene linker to: Q, a targeting moiety, an analyte molecule, a solid support, a solid support residue, a nucleoside or a further compound of structure (I) or a further compound of structure (II). In some embodiments, L′ comprises an alkylene oxide or phosphodiester moiety, or combinations thereof. In certain embodiments, L′ has the following structure:

wherein:

m″ and n″ are independently an integer from 1 to 10;

R^(e) is H, an electron pair or a counter ion;

L″ is R^(e) or a direct bond or linkage to: Q, a targeting moiety, an analyte molecule, a solid support, a solid support residue, a nucleoside or a further compound of structure (I) or a further compound of structure (II).

In still other embodiments, Q is, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with an analyte molecule or a solid support. In other embodiments, Q is, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with a complementary reactive group Q′. For example, in some embodiments, Q′ is present on a further compound of structure (I) or structure (II) (e.g., in the R² or R³ position), and Q and Q′ comprise complementary reactive groups such that reaction of the compound of structure (I) or structure (II) and the further compound of structure (I) or structure (II) results in covalently bound dimer of the compound of structure (I) or structure (II). Multimer compounds of structure (I) or structure (II) can also be prepared in an analogous manner and are included within the scope of embodiments of the invention.

The type of Q group and connectivity of the Q group to the remainder of the compound of structure (I) or structure (II) is not particularly limited, provided that Q comprises a moiety having appropriate reactivity for forming the desired bond.

In certain embodiments, Q is a moiety which is not susceptible to hydrolysis under aqueous conditions, but is sufficiently reactive to form a bond with a corresponding group on an analyte molecule or solid support (e.g., an amine, azide or alkyne).

Certain embodiments of compounds of structure (I) and/or structure (II) comprise Q groups commonly employed in the field of bio-conjugation. For example in some embodiments, Q comprises a nucleophilic reactive group, an electrophilic reactive group or a cycloaddition reactive group. In some more specific embodiments, Q comprises a sulfhydryl, disulfide, activated ester, isothiocyanate, azide, alkyne, alkene, diene, dienophile, acid halide, sulfonyl halide, phosphine, α-haloamide, biotin, amino or maleimide functional group. In some embodiments, the activated ester is an N-succinimide ester, imidoester or polyflourophenyl ester. In other embodiments, the alkyne is an alkyl azide or acyl azide. In some embodiments, Q comprises a maleimide functional group.

Exemplary Q moieties are provided in Table I below.

TABLE 1 Exemplary Q Moieties Structure Class

Sulfhydryl

Isothiocyanate

Imidoester

Acyl Azide

Activated Ester

Activated Ester

Activated Ester

Activated Ester

Activated Ester

Activated Ester

Sulfonyl halide

Maleimide

Maleimide

α-haloimide

Disulfide

Phosphine

Azide

Alkyne

Biotin

Diene

Alkene/dienophile

Alkene/dienophile —NH₂ Amino

It should be noted that in some embodiments, wherein Q is SH, the SH moiety will tend to form disulfide bonds with another sulfhydryl group on another compound of structure (I) or structure (II). Accordingly, some embodiments include compounds of structure (I), which are in the form of disulfide dimers, the disulfide bond being derived from SH Q groups. Other embodiments include compounds of structure (II), which are in the form of disulfide dimers, the disulfide bond being derived from SH Q groups.

In some other embodiments, one of R² or R³ is OH or —OP(═R_(a))(R_(b))R_(c), and the other of R² or R³ is a linker comprising a covalent bond to an analyte molecule or a linker comprising a covalent bond to a solid support. For example, in some embodiments the analyte molecule is a nucleic acid, amino acid or a polymer thereof. In other embodiments, the analyte molecule is an enzyme, receptor, receptor ligand, antibody, glycoprotein, aptamer or prion. In still different embodiments, the solid support is a polymeric bead or non-polymeric bead. In some embodiments, the targeting moiety is an antibody or cell surface receptor antagonist.

In certain specific embodiments, R² or R³ has one of the following structures:

The value for m is another variable that can be selected based on the desired distance between chromophores, fluorescence and/or color intensity. In some embodiments, m is, at each occurrence, independently an integer from 1 to 10. In other embodiments, m is, at each occurrence, independently an integer from 1 to 5, for example 1, 2, 3, 4 or 5.

The fluorescence intensity can also be tuned by selection of different values of n. In certain embodiments, n is an integer from 1 to 100. In other embodiments, n is an integer from 1 to 10.

M¹ and M² are selected based on the desired optical properties, for example based on a desired Stoke's shift, absorbance/emission overlap, a particular color and/or fluorescence emission wavelength. In some embodiments, M¹ (or alternatively M²) is the same at each occurrence; however, it is important to note that each occurrence of M¹ or M² need not be an identical M¹ or M², respectively. Certain embodiments include compounds wherein M¹ is not the same at each occurrence. Some embodiments include compounds wherein M² is not the same at each occurrence.

In some embodiments M¹ and M² are selected to have absorbance and/or emission characteristics for use in FRET methods. For example, in such embodiments the different M¹ and M² moieties are selected such that M¹ has an absorbance of radiation at one wavelength that induces an emission of radiation by M² at a different wavelength by a FRET mechanism. Exemplary M¹ and M² moieties can be appropriately selected by one of ordinary skill in the art based on the desired end use.

Each respective M¹ and M² may be attached to the remainder of the molecule from any position (i.e., atom) on M¹ or M². One of skill in the art will recognize means for attaching M¹ or M² to the remainder of molecule. Exemplary methods include the “click” reactions described herein.

In some embodiments, M¹ or M² are FRET, fluorescent or colored moieties. Any fluorescent and/or colored moiety may be used to form a FRET donor-acceptor pair, for examples those known in the art and typically employed in colorimetric, UV, and/or fluorescent assays may be used. In some embodiments, M¹ or M², or both are, at each occurrence, independently fluorescent or colored. Examples of M¹ or M² moieties which are useful in various embodiments of the invention include, but are not limited to: Xanthene derivatives (e.g., fluorescein, rhodamine, Oregon green, eosin or Texas red); Cyanine derivatives (e.g., cyanine, indocarbocyanine, oxacarbocyanine, thiacarbocyanine or merocyanine); Squaraine derivatives and ring-sub stituted squaraines, including Seta, SeTau, and Square dyes; Naphthalene derivatives (e.g., dansyl and prodan derivatives); Coumarin derivatives; oxadiazole derivatives (e.g., pyridyloxazole, nitrobenzoxadiazole or benzoxadiazole); Anthracene derivatives (e.g., anthraquinones, including DRAQS, DRAQ7 and CyTRAK Orange); Pyrene derivatives such as cascade blue; Oxazine derivatives (e.g., Nile red, Nile blue, cresyl violet, oxazine 170); Acridine derivatives (e.g., proflavin, acridine orange, acridine yellow); Arylmethine derivatives: auramine, crystal violet, malachite green; and Tetrapyrrole derivatives (e.g., porphin, phthalocyanine or bilirubin). Other exemplary M moieties include: Cyanine dyes, xanthate dyes (e.g., Hex, Vic, Nedd, Joe or Tet); Yakima yellow; Redmond red; tamra; texas red and alexa fluor® dyes.

In still other embodiments of any of the foregoing, M¹ or M², or both, at each occurrence, independently comprise three or more aryl or heteroaryl rings, or combinations thereof, for example four or more aryl or heteroaryl rings, or combinations thereof, or even five or more aryl or heteroaryl rings, or combinations thereof. In some embodiments, M¹ or M², or both, at each occurrence, independently comprise six aryl or heteroaryl rings, or combinations thereof. In further embodiments, the rings are fused. For example in some embodiments, M¹ or M² or both, at each occurrence, independently comprise three or more fused rings, four or more fused rings, five or more fused rings, or even six or more fused rings.

In some embodiments, M¹ or M² or both, are cyclic. For example, in some embodiments M¹ or M² or both, are carbocyclic. In other embodiment, M¹ or M² or both are heterocyclic. In still other embodiments of the foregoing, M¹ or M² or both, at each occurrence, independently comprise an aryl moiety. In some of these embodiments, the aryl moiety is multicyclic. In other more specific examples, the aryl moiety is a fused-multicyclic aryl moiety, for example which may comprise at least 3, at least 4, or even more than 4 aryl rings.

In other embodiments of any of the foregoing compounds of structure (I), (II), (IA), (IB), (IC), (ID), or (IE) M¹ or M² or both, at each occurrence, independently comprise at least one heteroatom. For example, in some embodiments, the heteroatom is nitrogen, oxygen or sulfur.

In still more embodiments of any of the foregoing, M¹ or M² or both, at each occurrence, independently comprise at least one substituent. For example, in some embodiments the substituent is a fluoro, chloro, bromo, iodo, amino, alkylamino, arylamino, hydroxy, sulfhydryl, alkoxy, aryloxy, phenyl, aryl, methyl, ethyl, propyl, butyl, isopropyl, t-butyl, carboxy, sulfonate, amide, or formyl group.

In some even more specific embodiments of the foregoing, M¹ or M² or both are, at each occurrence, independently a dimethylaminostilbene, quinacridone, fluorophenyl-dimethyl-BODIPY, his-fluorophenyl-BODIPY, acridine, terrylene, sexiphenyl, porphyrin, benzopyrene, (fluorophenyl-dimethyl-difluorobora-diaza-indacene)phenyl, (bis-fluorophenyl-difluorobora-diaza-indacene)phenyl, quaterphenyl, bi-benzothiazole, ter-benzothiazole, bi-naphthyl, bi-anthracyl, squaraine, squarylium, 9, 10-ethynylanthracene or ter-naphthyl moiety. In other embodiments, M¹ or M² or both are, at each occurrence, independently p-terphenyl, perylene, azobenzene, phenazine, phenanthroline, acridine, thioxanthrene, chrysene, rubrene, coronene, cyanine, perylene imide, or perylene amide or a derivative thereof. In still more embodiments, M¹ or M² or both are, at each occurrence, independently a coumarin dye, resorufin dye, dipyrrometheneboron difluoride dye, ruthenium bipyridyl dye, energy transfer dye, thiazole orange dye, polymethine or N-aryl-1,8-naphthalimide dye. In certain embodiments, M¹ and M² are, at each occurrence, independently boron-dipyrromethene, rhodamine, cyanine, pyrene, perylene, perylene monoimide or 6-FAM or a derivative thereof.

In still more embodiments of any of the foregoing, M¹ at each occurrence is the same. In other embodiments, each M¹ is different. In still more embodiments, one or more M¹ is the same and one or more M¹ is different.

In still more embodiments of any of the foregoing, M² at each occurrence is the same. In other embodiments, each M² is different. In still more embodiments, one or more M² is the same and one or more M² is different.

In some embodiments, M¹ or M² or both are, at each occurrence, independently boron-dipyrromethene, rhodamine, cyanine, pyrene, perylene, perylene monoimide or 6-FAM or a derivative thereof. In some other embodiments, M¹ and M² at each occurrence, independently have one of the following structures:

In some specific embodiments, the compound is a compound selected from Table 2. In other specific embodiments, the compound is a compound selected from Table 3. The compounds in Tables 2 and 3 were prepared according to the procedures set forth in the Examples and their identity confirmed by mass spectrometry.

TABLE 2 Exemplary Compounds of Structure I MW. Found Nos. Calc. Structure I-1  2049.9 2049.3

I-2  2394.1 2393.6

I-3  2738.3 2737.9

I-4  3082.4 3084.0

I-5  2258.3 2260.2

I-6  2602.7 2604.5

I-7  2947.3 2948.8

I-8  3291.7 3293.1

I-9  5578.9 5578.5

I-10 8420.7 8418.9

I-11 11260.4  11259.2 

I-12 14102.4  14009.5 

I-13 3634.2 3633.8

I-14 4322.7 4322.4

I-15 3882.3 3881.9

I-16 3369.6 3369.5

I-17 3794.2 3793.8

I-18 3305.9 3305.5

I-19 3666.4 3665.8

I-20 4891.3 4889.9

I-21 5235.2 5234.2

I-22 5580.3 5578.5

I-23 5924.9 5922.8

I-24 4909.5 4911.1

I-25 1858.2 1858.5

I-26 2202.8 2202.8

I-27 2546.7 2547.1

I-28 2891.8 2891.4

I-29 2173.8 2173.4

I-30 2297.7 2297.4

I-31 2421.6 2421.5

I-32 2546.0 2545.5

I-33 3994.9 3994.0

I-34 5251.3 5250.1

I-35 6508.2 6506.2

I-36 7764.2 7762.3

I-37 2489.3 2489.0

I-38 3745.3 3745.1

I-39 5002.3 5001.2

I-40 6257.8 6257.3

I-41 6048.1 6046.9

I-42 5827.6 5826.6

I-43 5952.2 5950.7

I-44 6075.4 6074.7

I-45 2809.4 2812.7

I-46 4465.5 4471.4

I-47 — 6130.2

I-48 — 7788.9

I-49  937.4  937.8

I-50 1289.7 1290.2

I-51  987.3  987.9

I-52 1389.8 1390.3

I-53 2359.6 2360.2

I-54 3329.7 3330.1

I-55 4300.8 4300.0

I-56 2209.6 2210.0

I-57 3129.3 3129.9

I-58 4049.2 4049.7

I-59 4969.2 4969.5

TABLE 3 Exemplary Compounds of Structure II MW. Found Nos. Calc. Structure II-1 1538.6 1538.3

II-2 1786.0 1785.8

II-3 1111.3 1112.0

II-4 1235.4 1236.0

II-5 1856.0 1856.3

II-6 1979.8 1980.3

II-7 2104.0 2104.4

II-8 2227.8 2228.4

As used in Tables 2 and 3 above and throughout this disclosure, F and F′ refer to a fluorescein moiety have the following structures, respectively:

As used in Tables 2 and 3 above and throughout this disclosure dT refers to the following structure:

wherein:

R is H or a direct bond.

As used in Tables 2 and 3 above and throughout this disclosure, B and B′ refer to the following structures, respectively:

As used in Tables 2 and 3 above and throughout this disclosure, T refers to the following structure:

As used in Tables 2 and 3 above and throughout this disclosure, C refers to the following structure:

As used in Tables 2 and 3 above and throughout this disclosure, Y refers to the following structure:

Alternatively, for any of the embodiments of F, F′, B, B′, C, and Y disclosed herein, the oxo moiety

may be replaced with a direct bond to the remainder of the molecule. In some of the foregoing embodiments, L¹ is alkylene, e.g., methylene or ethylene.

The presently disclosed dye combinations are “tunable,” meaning that by proper selection of the variables in any of the foregoing compounds, one of skill in the art can arrive at a compound having a desired and/or predetermined FRET properties (e.g., fluorescence emission signal, Stoke's shift). The “tunability” of the compounds allows the user to easily arrive at compounds having the desired Stoke's shift, fluorescence signal and/or color for use in a particular assay or for identifying a specific analyte of interest. Although all variables may have an effect on the FRET properties of the compounds, proper selection of M¹, M², L⁴, m and n is believed to play an important role in the molar fluorescence of the compounds. Accordingly, in one embodiment is provided a method for obtaining a compound having a desired FRET fluorescence properties, the method comprising selecting M¹ and M² moieties having known interactive properties, preparing a compound of structure (I) or (II) comprising the M¹ and M² moieties, and selecting the appropriate variables for L⁴, m and n to arrive at the desired FRET properties (e.g., Stoke's shift, reduction of donor emission signal).

FRET fluorescence emission signal in certain embodiments can be expressed in terms of the fold increase or decrease relative to the FRET fluorescence emission signal of the parent fluorophore(s) (e.g., monomers). In some embodiments the FRET fluorescence emission signal of the present compounds is 1.1×, 1.5×, 2×, 3×, 4×, 5×, 6×, 7×, 8×, 9×, 10×, or greater than 10× relative to the parent chromophore(s)/fluorophore(s). Various embodiments include preparing compounds having the desired fold increase in fluorescence relative to the parent fluorophore by proper selection of L⁴, m and n.

For ease of illustration, various compounds comprising phosphorous moieties (e.g., phosphate and the like) are depicted in the anionic state (e.g., —OPO(OH)O⁻, —OPO₃ ²⁻). One of skill in the art will readily understand that the charge is dependent on pH and the uncharged (e.g., protonated or salt, such as sodium or other cation) forms are also included in the scope of embodiments of the invention.

Compositions comprising any of the foregoing compounds and one or more analyte molecules (e.g., biomolecules) are provided in various other embodiments. In some embodiments, use of such compositions in analytical methods for detection of the one or more analyte molecules is also provided.

In still other embodiments, the compounds are useful in various analytical methods. For example, in certain embodiments the disclosure provides a method of staining a sample, the method comprising adding to said sample a compound of any of the foregoing embodiments (e.g., a compound of structure (I) or (II)), in an amount sufficient to produce an optical response when said sample is illuminated at an appropriate wavelength.

In some embodiments of the foregoing methods, R² is a linker comprising a covalent linkage to an analyte molecule, such as a biomolecule. For example, a nucleic acid, amino acid or a polymer thereof (e.g., polynucleotide or polypeptide). In still more embodiments, the biomolecule is an enzyme, receptor, receptor ligand, antibody, glycoprotein, aptamer or prion.

In yet other embodiments of the foregoing method, R² is a linker comprising a covalent linkage to a solid support such as a microparticle. For example, in some embodiments the microparticle is a polymeric bead or non-polymeric bead.

In even more embodiments, the optical response is a fluorescent response.

In other embodiments, said sample comprises cells, and some embodiments further comprise observing said cells by flow cytometry.

In still more embodiments, the method further comprises distinguishing the fluorescence response from that of a second fluorophore having detectably different optical properties.

In other embodiments, the disclosure provides a method for visually detecting an analyte molecule, such as a biomolecule, comprising:

-   -   (a) providing a polymer compound according to the foregoing         embodiments (e.g., structure (I) or structure (II)), wherein the         polymer compound comprises covalent bond to the analyte molecule         (e.g., one of R² or R³ is a linker comprising a covalent bond to         the analyte molecule, and the other of R² or R³ is H, OH, alkyl,         alkoxy, alkylether or —OP(═R_(a))(R_(b))R_(c)); and     -   (b) detecting the compound by its visible properties.

In some embodiments the analyte molecule is a nucleic acid, amino acid or a polymer thereof (e.g., polynucleotide or polypeptide). In still more embodiments, the analyte molecule is an enzyme, receptor, receptor ligand, antibody, glycoprotein, aptamer or prion.

In other embodiments, a method for visually detecting an analyte molecule, such as a biomolecule is provided, the method comprising:

(a) admixing any of the foregoing polymer compounds wherein the compound comprises a covalent bond to Q selected from Table 1, with the analyte molecules; and

(b) forming a bio-conjugate of the polymer compound and the analyte molecule; and

(c) detecting the bio-conjugate by its visible properties.

Some embodiments provide use of the composition in an analytical method for detection of the one or more analyte molecules.

In addition to the above methods, embodiments of the compounds of structure (I) and structure (II) find utility in various disciplines and methods, including but not limited to: imaging in endoscopy procedures for identification of cancerous and other tissues; single-cell and/or single molecule analytical methods, for example detection of polynucleotides with little or no amplification; cancer imaging, for example by conjugating a compound of structure (I) and structure (II) to an antibody or sugar or other moiety that preferentially binds cancer cells; imaging in surgical procedures; binding of histones for identification of various diseases; drug delivery, for example by replacing the M¹ and/or M² moiety in a compound of structure (I) and structure (II) with an active drug moiety; and/or contrast agents in dental work and other procedures, for example by preferential binding of the compound of structure (I) and structure (II) to various flora and/or organisms.

It is understood that any embodiment of the compounds of structure (I) and structure (II), as set forth above, and any specific choice set forth herein for a R¹, R², R³, R⁴, R⁵, L¹, L², L³, L⁴, M¹, M², m and/or n variable in the compounds of structures (I) or (II), as set forth above, may be independently combined with other embodiments and/or variables of the compounds of structures (I) or (II) to form embodiments of the invention not specifically set forth above. In addition, in the event that a list of choices is listed for any particular R¹, R², R³, R⁴, R⁵, L¹, L², L³, L⁴, M¹, M², m and/or n variable in a particular embodiment and/or claim, it is understood that each individual choice may be deleted from the particular embodiment and/or claim and that the remaining list of choices will be considered to be within the scope of the invention.

It is understood that in the present description, combinations of substituents and/or variables of the depicted formulae are permissible only if such contributions result in stable compounds.

It will also be appreciated by those skilled in the art that in the process described herein the functional groups of intermediate compounds may need to be protected by suitable protecting groups. Such functional groups include hydroxy, amino, mercapto and carboxylic acid. Suitable protecting groups for hydroxy include trialkylsilyl or diarylalkylsilyl (for example, t-butyldimethylsilyl, t-butyldiphenylsilyl or trimethylsilyl), tetrahydropyranyl, benzyl, and the like. Suitable protecting groups for amino, amidino and guanidino include t-butoxycarbonyl, benzyloxycarbonyl, and the like. Suitable protecting groups for mercapto include —C(O)—R″ (where R″ is alkyl, aryl or arylalkyl), p-methoxybenzyl, trityl and the like. Suitable protecting groups for carboxylic acid include alkyl, aryl or arylalkyl esters. Protecting groups may be added or removed in accordance with standard techniques, which are known to one skilled in the art and as described herein. The use of protecting groups is described in detail in Green, T. W. and P. G. M. Wutz, Protective Groups in Organic Synthesis (1999), 3rd Ed., Wiley. As one of skill in the art would appreciate, the protecting group may also be a polymer resin such as a Wang resin, Rink resin or a 2-chlorotrityl-chloride resin.

Furthermore, all compounds of the invention which exist in free base or acid form can be converted to their salts by treatment with the appropriate inorganic or organic base or acid by methods known to one skilled in the art. Salts of the compounds of the invention can be converted to their free base or acid form by standard techniques.

The following Reaction Schemes illustrate exemplary methods of making compounds of this invention. It is understood that one skilled in the art may be able to make these compounds by similar methods or by combining other methods known to one skilled in the art. It is also understood that one skilled in the art would be able to make, in a similar manner as described below, other compounds of structure (I) or (II) not specifically illustrated below by using the appropriate starting components and modifying the parameters of the synthesis as needed. In general, starting components may be obtained from sources such as Sigma Aldrich, Lancaster Synthesis, Inc., Maybridge, Matrix Scientific, TCI, and Fluorochem USA, etc. or synthesized according to sources known to those skilled in the art (see, for example, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 5th edition (Wiley, December 2000)) or prepared as described in this invention.

In particular, methods for preparing embodiments of the compounds disclosed herein (e.g., structures (I) and (II)) can be found, for example, in PCT Pub. Nos. WO 2015/027176, WO 2016/138461, WO 2016/183185, WO 2017/173348, WO 2017/173355, WO 2017/177065, WO 2017/196954, WO 2017/214165, and WO 2018/022925, each of which are hereby incorporated by reference in their entirety.

Reaction Scheme I illustrates an exemplary method for preparing an intermediate useful for preparation of compounds of structures (I) and (II), where R¹, L², and L³ are as defined above, R² and R³ are as defined above or are protected variants thereof and L is an optional linker. Referring to Reaction Scheme 1, compounds of structure a can be purchased or prepared by methods well-known to those of ordinary skill in the art. Reaction of a with M-X, where X is a halogen such as bromo, under Suzuki coupling conditions known in the art results in compounds of structure b. Compounds of structure b can be used for preparation of compounds of structures (I) or (II) as described below.

Reaction Scheme II illustrates an alternative method for preparation of intermediates useful for preparation of compounds of structures (I) and (II). Referring to reaction Scheme II, where R¹, L¹, L², L³, and G as defined above, and R² and R³ are as defined above or are protected variants thereof, a compound of structure c, which can be purchased or prepared by well-known techniques, is reacted with M-G′ to yield compounds of structure d. Here, G and G′ represent functional groups having complementary reactivity (i.e., functional groups which react to form a covalent bond). G′ may be pendant to M or a part of the structural backbone of M. G may be any number of functional groups described herein, such as an alkyne or amine.

The compound of structures (I) and (II) may be prepared from one of structures b or d by reaction under well-known automated DNA synthesis conditions with a phosphoramidite compound having the following structure (e):

wherein each L⁴ is independently an optional linker.

DNA synthesis methods are well-known in the art. Briefly, two alcohol groups, for example R² and R³ in intermediates b or d above, are functionalized with a dimethoxytrityl (DMT) group and a 2-cyanoethyl-N,N-diisopropylamino phosphoramidite group, respectively. The phosphoramidite group is coupled to an alcohol group, typically in the presence of an activator such as tetrazole, followed by oxidation of the phosphorous atom with iodine. The dimethoxytrityl group can be removed with acid (e.g., chloroacetic acid) to expose the free alcohol, which can be reacted with a phosphoramidite group. The 2-cyanoethyl group can be removed after oligomerization by treatment with aqueous ammonia.

Preparation of the phosphoramidites used in the oligomerization methods is also well-known in the art. For example, a primary alcohol (e.g., R³) can be protected as a DMT group by reaction with DMT-Cl. A secondary alcohol (e.g., R²) is then functionalized as a phosphoramidite by reaction with an appropriate reagent such as 2-cyanoethyl N,N-dissopropylchlorophosphoramidite. Methods for preparation of phosphoramidites and their oligomerization are well-known in the art and described in more detail in the examples.

Compounds of structures (I) or (II) are prepared by oligomerization of intermediates b or d and e according to the well-known phophoramidite chemistry described above. The desired number of m and n repeating units is incorporated into the molecule by repeating the phosphoramidite coupling the desired number of times. It will be appreciated that compounds of structure (III) as, described below, can be prepared by analogous methods.

In various other embodiments, compounds useful for preparation of the compound of structures (I) or (II) are provided. The compounds can be prepared as described above in monomer, dimer and/or oligomeric form and then the M¹ and/or M² moieties covalently attached to the compound via any number of synthetic methodologies (e.g., the “click” reactions described above) to form compounds of structures (I) or (II). Accordingly, in various embodiments a compound is provided having the following structure (III):

or a stereoisomer, salt or tautomer thereof, wherein:

G¹ and G² are, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with a complementary reactive group;

L^(1a) and L^(1b) are, at each occurrence, an optional linker;

L² and L³ are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;

L⁴ is, at each occurrence, independently an alkylene or heteroalkylene linker;

R¹ is, at each occurrence, independently H, alkyl or alkoxy;

R² and R³ are each independently H, OH, SH, alkyl, alkoxy, alkylether, —OP(═R_(a))(R_(b))R_(c), Q, a linker comprising a covalent bond to Q, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support or a linker comprising a covalent bond to a further compound of structure (II), wherein: R_(a) is O or S; R_(b) is OH, SH, O⁻, S⁻, OR_(d) or SR_(d); R_(c) is OH, SH, O⁻, S⁻, OR_(d), SR_(d), alkyl, alkoxy, alkylether , alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether; and R_(d) is a counter ion;

R⁴ is, at each occurrence, independently OH, SH, O⁻, S⁻, OR_(a) or SR_(d);

R⁵ is, at each occurrence, independently oxo, thioxo or absent;

Q is, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with an analyte molecule, a solid support or a complementary reactive group Q′;

m is, at each occurrence, independently an integer of zero or greater, provided that at least one occurrence of m is an integer of one or greater; and

n is an integer of one or greater.

In various embodiments a compound is provided having the following structure (IV):

or a stereoisomer, salt or tautomer thereof, wherein:

G¹ and G² are, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with a complementary reactive group;

L^(1a) and L^(1b) are, at each occurrence, independently an optional linker;

L² and L³ are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;

L⁴ is, at each occurrence, independently an alkylene or heteroalkylene linker;

R¹ is, at each occurrence, independently H, alkyl or alkoxy;

R² and R³ are each independently H, OH, SH, alkyl, alkoxy, alkylether, —OP(═R_(a))(R_(b))R_(c), Q, a linker comprising a covalent bond to Q, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support or a linker comprising a covalent bond to a further compound of structure (II), wherein: R_(a) is O or S; R_(b) is OH, SH, O⁻, S⁻, OR_(d) or SR_(d); R_(c) is OH, SH, O⁻, S⁻, OR_(d), SR_(d), alkyl, alkoxy, alkylether, alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether; and R_(d) is a counter ion;

R⁴ is, at each occurrence, independently OH, SH, O⁻, S⁻, OR_(d) or SR_(d);

R⁵ is, at each occurrence, independently oxo, thioxo or absent;

Q is, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with an analyte molecule, a solid support or a complementary reactive group Q′;

m is, at each occurrence, independently an integer of zero or greater, provided that at least one occurrence of m is an integer of one or greater; and

n is an integer of one or greater.

G¹ and G² moieties in the compound of structures (III) and (IV) can be selected from any moiety comprising a group having the appropriate reactivity group for forming a covalent bond with a complementary group on an M¹ or M² moiety. In exemplary embodiments, the G¹ and G² moieties can be selected from any of the Q moieties described herein, including those specific examples provided in Table 1. In some embodiments, G¹ or G² or both comprise, at each occurrence, independently a moiety suitable for reactions including: the copper catalyzed reaction of an azide and alkyne to form a triazole (Huisgen 1, 3-dipolar cycloaddition), reaction of a diene and dienophile (Diels-Alder), strain-promoted alkyne-nitrone cycloaddition, reaction of a strained alkene with an azide, tetrazine or tetrazole, alkene and azide [3+2] cycloaddition, alkene and tetrazine inverse-demand Diels-Alder, alkene and tetrazole photoreaction and various displacement reactions, such as displacement of a leaving group by nucleophilic attack on an electrophilic atom.

In some embodiments, G¹ or G² or both are, at each occurrence, independently a moiety comprising an aldehyde, oxime, hydrazone, alkyne, amine, azide, acylazide, acylhalide, nitrile, nitrone, sulfhydryl, disulfide, sulfonyl halide, isothiocyanate, imidoester, activated ester, ketone, α,β-unsaturated carbonyl, alkene, maleimide, α-haloimide, epoxide, aziridine, tetrazine, tetrazole, phosphine, biotin or thiirane functional group.

In other embodiments, G¹ or G² or both comprise, at each occurrence, independently an alkyne or an azide group. In different embodiments, G¹ or G² or both comprise, at each occurrence, independently a reactive group capable of forming a functional group comprising an alkene, ester, amide, thioester, disulfide, carbocyclic, heterocyclic or heteroaryl group, upon reaction with the complementary reactive group. For example, in some embodiment the heteroaryl is triazolyl.

In various other embodiments of the compound of structures (III) and (IV), L² and L³ are, at each occurrence, independently C₁-C₆ alkylene, C₂-C₆ alkenylene or C₂-C₆ alkynylene.

In other embodiments of structures (III) and (IV), each L^(1a) is absent. In other embodiments, each L^(1a) is present, for example L^(1a) is, at each occurrence, independently heteroalkylene. In certain embodiments, L^(1a) has the following structure:

In other of any of the foregoing embodiments of structures (III) and (IV), G¹ or G² or both is, at each occurrence, independently

In various embodiments, G¹ alkynyl at each occurrence, such as ethynyl and G² is —NH₂. In other embodiments, G¹ is an azide at each occurrence and G² is —NH₂ at each occurrence.

In various embodiments, G² alkynyl at each occurrence, such as ethynyl and G¹ is —NH₂. In other embodiments, G² is an azide at each occurrence and G¹ is —NH₂ at each occurrence.

The efficiency of the FRET process depends, in part, on characteristics of the chromophores. Specifically, high efficiency FRET requires a large overlap between the absorbance spectrum of the donor chromophore and the emission spectrum of the acceptor chromophore. Additionally, the distance and orientation of the chromophores plays an important role. FRET efficiency is inversely proportional to the 6^(th) power of the distance between the chromophores and the angle of the transition dipole moment should substantially align to be parallel (i.e., be near to 0° or)180°. Accordingly, in certain embodiments, covalent attachments of a first and a second chromophore to the polymer backbone are selected so distance between the first and second chromophore is minimized and transition dipole moments substantially align. The efficiency of FRET can be expressed according to the following equation:

$E_{{FRET} =}\frac{Ro^{6}}{{Ro^{6}} + R^{6}}$

wherein E_(FRET) is FRET efficiency, R is the distance between chromophores, and Ro is expressed according to the following equation:

Ro=(8.8×10²³ JK ² Q _(o) n ⁻⁴)^(1/6)

wherein J is the spectral overlap of the absorbance spectrum of the acceptor and the emission spectrum of the donor, Q_(o) is donor quantum efficiency, n⁻⁴ is the index of medium between the donor and acceptor (constant), and K² is the dipole directions matching.

Accordingly, one embodiment provides a polymer compound comprising an acceptor chromophore having an acceptor transition dipole moment and being covalently linked to a polymer backbone, and a donor chromophore having a donor transition dipole moment and being covalently linked to the polymer backbone, wherein the polymer compound adopts a confirmation in solution at physiological conditions wherein the effective distance between the acceptor chromophore and the donor chromophore is less than about 50.0 nm and the acceptor transition dipole and the donor transition dipole are substantially parallel.

In some embodiments, the effective distance between the acceptor chromophore and the donor chromophore is less than about 25.0 nm. In some embodiments, the effective distance between the acceptor chromophore and the donor chromophore is less than about 10.0 nm. In some embodiments, the effective distance between the acceptor chromophore and the donor chromophore is less than about 30.0 nm, less than about 27.0 nm, less than about 22.0 nm, less than about 20.0 nm, less than about 17.0 nm, less than about 15.0 nm, less than about 12.0 nm, less than about 11.0 nm, less than about 9.0 nm, less than about 8.0 nm, less than about 7.0 nm, less than about 6.0 nm, less than about 5.0 nm, less than about 4.0 nm, less than about 3.0 nm, less than about 2.0 nm, or less than about 1.0 nm.

In some embodiments, the acceptor chromophore is a fluorescent dye moiety. In certain embodiments, the donor chromophore is a fluorescent dye moiety. In certain related embodiments, the acceptor chromophore and the donor chromophore are both fluorescent dye moieties.

In some embodiments, the angle between the acceptor transition dipole moment and the donor transition dipole moment ranges from 120° to 180°. For example, in some embodiments, the angle between the acceptor transition dipole moment and the donor transition dipole moment ranges from 125° to 180°, from 130° to 180°, from 140° to 180°, from 150° to 180°, from 160° to 180°, from 170° to 180°, from 172° to 180°, from 175° to 180°, or from 177° to 180°.

In certain embodiments, the angle between the acceptor transition dipole moment and the donor transition dipole moment ranges from 0° to 60°. For example, For example, in some embodiments, the angle between the acceptor transition dipole moment and the donor transition dipole moment ranges from 0° to 50°, from 0° to 40°, from 0° to 30°, from 0° to 20°, from 0° to 10°, from 0° to 8°, from 0° to 5°, from 0° to 3°, or from 0° to 2°.

In some more specific embodiments, the polymer compound further comprises a first acceptor chromophore is covalently linked at a proximal end of the polymer backbone, a second acceptor chromophore is covalently linked at a distal end of the polymer backbone, and a donor chromophore is covalently linked between the proximal and distal ends of the polymer backbone.

In certain embodiments, the polymer backbone comprises a phosphate linker. In some embodiments, the polymer backbone comprises a plurality of phosphate linkers.

In some related embodiments, the polymer backbone comprises an alkylene oxide linker. In some more specific embodiments, the alkylene oxide is ethylene oxide. In some specific embodiments, the polymer backbone comprises a HEG linker, a C linker or combinations thereof.

In some embodiments, the polymer compound has a molecular weight less than 20,000 g/mol. In some embodiments, the polymer compound has a molecular weight less than 19,000 g/mol, 18,500 g/mol, 18,000 g/mol, 17,500 g/mol, 17,000 g/mol, 16,500 g/mol, 16,000 g/mol, 15,500 g/mol, 15,000 g/mol, 14,500 g/mol, 14,000 g/mol, 13,500 g/mol, 13,000 g/mol, 12,500 g/mol, 11,500 g/mol, 11,000 g/mol, 10,500 g/mol, 10,000 g/mol, 9,500 g/mol, 9,000 g/mol, 8,500 g/mol, 8,000 g/mol, 7,500 g/mol, 7,000 g/mol, 6,500 g/mol, 6,000 g/mol, 5,500 g/mol, 5,000 g/mol, 4,500 g/mol, 4,000 g/mol, 3,500 g/mol, 3,000 g/mol, 2,500 g/mol, 2,000 g/mol, 1,500 g/mol, or 1,000 g/mol.

In some embodiments the polymer compound is not a peptide or protein. In some other embodiments, the polymer backbone has no amide bonds.

The following Examples are provided for purposes of illustration, not limitation.

EXAMPLES General Methods

Mass spectral analysis was performed on a Waters/Micromass Quattro micro MS/MS system (in MS only mode) using MassLynx 4.1 acquisition software. Mobile phase used for LC/MS on dyes was 100 mM 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), 8.6 mM triethylamine (TEA), pH 8. Phosphoramidites and precursor molecules were also analyzed using a Waters Acquity UHPLC system with a 2.1mm×50mm Acquity BEH-C18 column held at 45° C., employing an acetonitrile/water mobile phase gradient. Molecular weights for monomer intermediates were obtained using tropylium cation infusion enhanced ionization on a Waters/Micromass Quattro micro MS/MS system (in MS only mode). Excitation and emission profiles experiments were recorded on a Cary Eclipse spectra photometer.

All reactions were carried out in oven dried glassware under a nitrogen atmosphere unless otherwise stated. Commercially available DNA synthesis reagents were purchased from Glen Research (Sterling, Va.). Anhydrous pyridine, toluene, dichloromethane, diisopropylethyl amine, triethylamine, acetic acid, pyridine, and THF were purchased from Aldrich. All other chemicals were purchase from Aldrich or TCI and were used as is with no additional purification.

Example 1 Synthesis of Polymer Backbone and Derivatization Synthesis of Representative Amine/Alkyne Polymer Compounds

Polymers were synthesized using an Applied Biosystems 394 DNA/RNA synthesizer on a 0.5-1 μmol scale. The polymer compounds were synthesized directly on CPG beads or a polystyrene solid support. Synthesis was carried out in the 3′ to 5′ direction using standard solid phase DNA synthetic methodology (i.e., β-cyanoethyl phosphoramidite coupling chemistry). Monomer reagents (e.g., Fluoroside phosphoramidites, C₂ alkyl phosphoramidite, hexaethylene glycol phosphoramidite, amino phosphoramidites, and alkyne phosphoramidites) were dissolved in acetonitrile and dichloromethane to make a 0.1 M stock solution. Monomer reagents were added in successive order using the following synthesis cycle:

1) removal of the 5′-dimethoxytrityl protecting group with dichloroacetic acid in dichloromethane or toluene;

2) coupling the next phosphoramidite monomer reagent with activator reagent (0.2 M ETT) in acetonitrile;

3) oxidation of phosphate (III) to form stable phosphate (V) with iodine/pyridine/water; and

4) capping unreacted 5′-hydroxyl groups with acetic anhydride/1-methylimidizole/acetonitrile.

The synthesis cycle was repeated until the desired polymer compound was assembled. Upon completion, the terminal monomethoxytrityl (MMT) group or dimethoxytrityl (DMT) group was removed using dichloroacetic acid in dichloromethane or toluene. Following synthesis, the support was treated with 20% diethylamine in acetonitrile for 15 minutes.

The representative amine polymers were then cleaved from the solid support using concentrated aqueous ammonium hydroxide at 55 ° C. for 2 hours. Constructs were characterized by ESI-MS to confirm mass and purity. Concentration was determined by UV.

Chromophore Coupling to Amine/Alkyne Polymer Compounds

Representative polymer constructs were synthesized to have orthogonal reactive groups (e.g., amine and alkyne) so distinct dyes moieties could be added. For instance, click chemistry was used to attach a first fluorophore to alkynes of the polymer.

A 100 mM sodium ascorbate solution and 500 mM phosphate buffer pH 7.6 were prepared. A first desired dye moiety comprising an azide functional group was dissolved in dimethyl sulfoxide at a concentration of 100 mM (“dye solution”).

The 100 mM sodium ascorbate solution (i.e., a 2.5:1:1 mixture of 100 mM sodium ascorbate/100 mM THTPA/50 mM copper sulfate) was prepared by adding equal volumes of THTPA and copper sulfate and allowing the mixture to sit for 5-10 minutes followed by the addition of sodium ascorbate.

The phosphate buffer, dye solution, polymer compound and extra DMSO were mixed together followed by the sodium ascorbate solution. Reactions were prepared having final polymer concentration of 0.5 mM, phosphate buffer concentration of 100 mM, 50-60% DMSO and 5-10 fold excess dye. Reactions were placed in the dark overnight on a rotator or vortex. Samples were diluted with water and desalted using G-25 Sephadex resin. Samples were collected and characterized by ESI-MS to confirm mass and purity. Following sample analysis the polymer compounds were lyophilized.

Addition of a second desired dye moiety (e.g., fluorophore or other label) to representative polymer compounds was achieved using NHS-ester/amine coupling chemistry. A sodium tetraborate buffer pH 9 stock solution (“borate buffer”) was initially prepared. A second dye moiety comprising an NHS-ester was dissolved at a concentration of 100-200 mM in DMSO. Reactions were prepared to have a polymer concentration of 1-2 mM, a borate buffer concentration of 100 mM, 30-75% DMSO and a 5-10-fold excess of dye. Reactions were placed in the dark overnight on a rotator or vortex. Samples were diluted with water and desalted using G-25 Sephadex resin. Samples were collected and characterized by ESI-MS to confirm mass and purity. Additionally, characterization by UV and fluorescence spectroscopy was used to determine FRET properties.

Example 2 Optimization of Polymer Backbone Length Between Chromophores—Test 1

Variation in the length polymer backbone between pendant chromophores was compared to determine the optimum spacer length (i.e., number hexaethylene glycol or “HEG” units).

Solutions were prepared at a concentration of 100 mM for Compounds I-1, I-2, I-3, and I-4. The emission spectrum for each sample was detected using an excitation wavelength of 494 nm. The experimental results indicate that the optimum spacing for this combination (i.e., a BODIPY-TMR and 6-FAM) is a spacer of two hexaethylene glycol units. The experimental results shown in FIG. 1 indicate the donor emission signal is minimized and the acceptor emission signal is relatively high. The molecular modeling calculations were substantially consistent with experimental data, except for the trans version of Compound I-1.

Example 3 Optimization of Polymer Backbone Length Between Chromophores—Test 2

Representative polymer compounds were tested, each having a FAM chromophore (FRET donor) and a Texas Red chromophore (FRET acceptor). The representative polymer compounds were compared to determine the optimum spacer length.

Solutions were prepared at a concentration of 200 nM for Compounds I-5, I-6, I-7 and I-8 and a pH of 7.0. The emission spectrum for each sample was detected using an excitation wavelength of 488 nm (emission detected at 620 nm). The results are shown in FIG. 2. The data suggest that the length of the spacer between the respective chromophores does not necessarily show higher FRET efficiency. For this combination (i.e., FAM and Texas Red), the molecular modeling calculations are substantially consistent with the experimental results.

Example 4 Donor Emission Characterization

Polymer compounds were prepared to determine the effect of relative positioning on brightness of the emission spectra of representative compounds. Representative sample polymers (i.e., Compounds I-9, I-10, I-11, and I-12) were prepared in a solution at a concentration of 100 nM and pH 7.0. Samples were tested using an excitation wavelength of 494 nm and the resultant spectra are shown in FIG. 3. As the data show, the donor emission signal is substantially similar to the acceptor emission signal detected for each of the respective samples.

Without wishing to be bound by theory, the present Applicants tried to optimize the spacing between the donor and acceptor chromophores and also position donor chromophores between acceptor chromophores along the polymer backbone. This strategy was used to reduce the donor emission signal while maintaining the signal strength of the acceptor chromophore. Samples with various spacer lengths and relative positions of acceptor and donor chromophores were prepared at a concentration of 500 nM at pH 7 and tested (i.e., Compounds I-13, I-14, I-15, I-16, I-17, I-18, and I-19), the results of which are shown in FIG. 4. Applicants unexpectedly found that positioning the donor chromophores between acceptor chromophores on the polymer backbone resulted in a significant reduction in the donor emission signal. Additionally, the optimum spacing length was discovered to be two hexaethylene glycol or “HEG” units as depicted in Compound I-14.

To further elucidate the relationship between chromophore spacing and relative emission signal strength, samples with variable numbers of HEG units were prepared and tested. Specifically, Compounds I-20, I-21, I-22, and I-23 were each prepared in a solution at a concentration of 5 μM at pH 7.2. The emission spectra for each respective compound are shown in FIG. 5.

Example 5 Synthesis of Tri-Valent Polymer Compounds

Representative polymer compounds were synthesized having three distinct chromophores. Polymer compounds were synthesized according to Example 1, with the addition of a FAM chromophore via an NHS/amine coupling, a BODIPY-TMR chromophore via an azide/alkyne coupling (i.e., a “click” reaction), and a Texas Red chromophore via an NHS/amine coupling. The desired product (i.e., Compound I-24) was confirmed by ESI-MS [M+H]⁺=4909.5.

The desired product was taken up in solution at a concentration of 5 μM at pH 7 and the absorbance spectrum was obtained. Absorbance peaks for FAM, BODIPY-TMR, and Texas Red were observed at approximately 510 nm, 540 nm, and 595 nm, respectively (FIG. 6). Solutions at pH 7 and pH 9 were used to determine the emission spectra of Compound I-24 (FIG. 7) showing FRET emission signals of the trivalent polymer compound for FAM, BODIPY-TMR, and Texas Red at approximately 515 nm, 575 nm and 610 nm, respectively.

All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including U.S. Provisional Patent Application No. 62/646,234, filed Mar. 21, 2018, are incorporated herein by reference, in their entirety to the extent not inconsistent with the present description.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

1. A compound having the following structure (I):

or a stereoisomer, salt or tautomer thereof, wherein: M¹ and M² are, at each occurrence, independently a fluorescent or colored chromophore, provided that at least one of M¹ and M² is a FRET donor, and another one of M¹ and M² is a corresponding FRET acceptor, and at least one of the FRET donor chromophores is positioned between two FRET acceptor chromophores; L¹ is, at each occurrence, independently an optional alkylene or heteroalkylene linker; L² and L³ are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker; L⁴ is, at each occurrence, independently an alkylene or heteroalkylene linker; R¹ is, at each occurrence, independently H, alkyl or alkoxy; R² and R³ are each independently H, OH, SH, alkyl, alkoxy, alkylether, heteroalkyl, −OP(═R_(a))(R_(b))R_(c), Q, or a protected form thereof, or L′; R⁴ is, at each occurrence, independently OH, SH, O⁻, S⁻ OR_(d) or SR_(d); R⁵ is, at each occurrence, independently oxo, thioxo or absent; R_(a) is O or S; R_(b) is OH, SH, O⁻, S⁻, OR_(d) or SR_(d); R_(c) is OH, SH, O⁻, S⁻, OR_(d), OL′, SR_(d), alkyl, alkoxy, heteroalkyl, heteroalkoxy, alkylether, alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether; R_(d) is a counter ion; Q is, at each occurrence, independently a moiety comprising a reactive group, or protected form thereof, capable of forming a covalent bond with an analyte molecule, a targeting moiety, a solid support or a complementary reactive group Q′; L′ is, at each occurrence, independently a linker comprising a covalent bond to Q, a linker comprising a covalent bond to a targeting moiety, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support, a linker comprising a covalent bond to a solid support residue, a linker comprising a covalent bond to a nucleoside or a linker comprising a covalent bond to a further compound of structure (I); m is, at each occurrence, independently an integer of zero or greater; and n is an integer of two or greater, provided that at least one occurrence of L⁴ is heteroalkylene or at least one occurrence of in is 0 when M¹ and M² are selected from fluorescein, pyrene and perylene chromophores. 2-7. (canceled)
 8. The compound of claim 1, wherein the compound has the following structure (IA):

wherein: z is, at each occurrence, independently an integer from 1 to 100; and m₁, m₂ and m₃ are, at each occurrence, independently an integer from 0 to
 6. 9. The compound of claim 1, wherein the compound has the following structure (1B):

wherein: z is, at each occurrence, independently an integer from 1 to
 100. 10. The compound of claim 1, wherein the compound has the following structure (IC):

wherein: x¹ x², x³ and x⁴ are, at each occurrence, independently an integer from 0 to
 6. 11-13. (canceled)
 14. The compound of claim 8, wherein the compound has the following structure (ID):


15. The compound of claim 1, wherein the compound has the following structure (IE):


16. A compound having the following structure (II):

or a stereoisomer, salt or tautomer thereof, wherein: M¹ and M² are, at each occurrence, independently a fluorescent or colored chromophore, provided that at least one occurrence of M¹ and M² combine to form a FRET acceptor-donor pair, and the FRET donor chromophore in the FRET acceptor-donor pair is positioned between two FRET acceptor chromophores; L¹ is at each occurrence, independently an optional alkylene or heteroalkviene linker; L² and L³ are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker; L⁴ is, at each occurrence, independently an alkylene or heteroalkylene linker; R¹ is, at each occurrence, independently H, alkyl or alkoxy; R² and R³ are each independently H, OH, SH, alkyl, alkoxy, alkylether, heteroalkyl, —OP(═R_(a))(R_(b))R_(c), Q, or a protected form thereof, or L′; R⁴ is, at each occurrence, independently OH, SH, O⁻, S⁻, OR_(d) or SR_(d); R⁵ is, at each occurrence, independently oxo, thioxo or absent; R_(a) is O or S; R_(b) is OH, SH, O⁻, S⁻, OR_(d) or SR_(d); R_(c) is OH, SH, O⁻, S⁻, OR_(d), OL′, SR_(d), alkyl, alkoxy, heteroalkyl, heteroalkoxy, alkylether, alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether; R_(d) is a counter ion; Q is, at each occurrence, independently a moiety comprising a reactive group, or protected form thereof, capable of forming a covalent bond with an analyte molecule, a targeting moiety, a solid support or a complementary reactive group Q′; L′ is, at each occurrence, independently a linker comprising a covalent bond to Q, a linker comprising a covalent bond to a targeting moiety, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support, a linker comprising a covalent bond to a solid support residue, a linker comprising a covalent bond to a nucleoside or a linker comprising a covalent bond to a further compound of structure (II); m is, at each occurrence, independently an integer of zero to two or greater than 6; and n is an integer of two or greater. 17-21. (canceled)
 22. The compound of claim 1, wherein for at least one occurrence of L¹, L¹-M has one of the following structures:

wherein L^(1a) and L^(1b) are each independently optional linkers. 23-26. (canceled)
 27. The compound of claim 22, wherein L^(1a) and L^(1b), when present, independently have one of the following structures:

28-29. (canceled)
 30. The compound of claim 1, wherein L¹ has one of the following structures:

wherein a, b, and c are each independently an integer ranging from 1-6.
 31. The compound of claim 1, wherein R⁴ is, at each occurrence, independently OH, O⁻ or OR_(d), R⁵ is at each occurrence, oxo, and R¹ is, at each occurrence, H. 32-34. (canceled)
 35. The compound of claim 1, wherein R² and R³ are each independently −OP(═R_(a))(R_(b))R_(c).
 36. The compound of claim 35, wherein Re is OL′.
 37. The compound of claim 36, wherein L′ is a heteroalkylene linker to: Q, a targeting moiety, an analyte molecule, a solid support, a solid support residue, a nucleoside or a further compound of structure (I).
 38. The compound of claim 37, wherein L′ comprises an alkylene oxide or phosphodiester moiety, or combinations thereof.
 39. The compound of claim 36, wherein L′ has the following structure:

wherein: m″ and n″ are independently an integer from 1 to 10; R^(e) is H, an electron pair or a counter ion; L″ is R^(e) or a direct bond or linkage to: Q, a targeting moiety, an analyte molecule, a solid support, a solid support residue, a nucleoside or a further compound of structure (I).
 40. (canceled)
 41. The compound of claim 1, wherein Q comprises a sulfhydryl, disulfide, activated ester, isothiocyanate, azide, alkyne, alkene, diene, dienophile, acid halide, sulfonyl halide, phosphine, α-haloamide, biotin, amino or maleimide functional group. 42-44. (canceled)
 45. The compound of claim 1, wherein Q has one of the following structures:

wherein each X is independently a halogen. 46-50. (canceled)
 51. The compound of claim 1, wherein R² or R³ has one of the following structures:

52-63. (canceled)
 64. The compound of claim 1, wherein M¹ and M² at each occurrence, independently have one of the following structures:


65. The compound of claim 1, wherein the compound has one of the following structures:

wherein HEG, R³, dT, B, B′, C, F, T and Y have the following structures, respectively:


66. The compound of claim 16, wherein the compound has one of the following structures:

wherein F and Y have the following structures respectively:

67-81. (canceled)
 82. A method of staining a sample, comprising adding to said sample the compound of claim 1 in an amount sufficient to produce an optical response when said sample is illuminated at an appropriate wavelength. 83-86. (canceled)
 87. A method for visually detecting an analyte molecule, the method comprising: (a) providing the polymer compound of claim 1, wherein the polymer compound comprises a covalent bond to the analyte molecule; and (b) detecting the polymer compound by its visible properties.
 88. A method for visually detecting an analyte molecule, the method comprising: (a) ad-mixing the polymer compound of claim 1, wherein the polymer compound comprises a covalent bond to Q, with the analyte molecule; (b) forming a bio-conjugate of the polymer compound and the analyte molecule; and (c) detecting the bio-conjugate by its visible properties. 89-90. (canceled) 